Stack switch



July 22, 1941- M. PERSONS STACK SWITCH Filed April 24, 1959 2 Sheets-Sheet l 7 7///V gm,

July 22, 1941. M. PERSONS STACK SWITCH Filed April 24, 1939 2 Sheets-Sheet 2 Patented July 22, 1941 STACK SWITCH Lawrence M. Persons, St. Louis Oounty,,Mo.. as-

signor to Automatic-Control Corporation, St. Louis, Mo., a corporation of Delaware Application April 24, 1939, Serial No. 269,634

4 Claims.

The present invention relates to stack switches and, in particular, to thermostats having heatresponsive units within some space, such as the stack, that is immediately responsive to any changes in heat conditions of a furnace and which thermostat operates a switch upon any change of the heat device within such critical space.

In particular, the stack switch is adapted to be connected in series with a room thermostat.

Objects of the invention include the provision of such a switch having an influencing unit displaceable in response to some external condition from position wherein it influences a control unit to a position wherein it does not influence the unit; and, specifically, the provision of a stack thermostat moving a heating unit toward or from a heat-responsive element so that the operation of the heat-responsive element is made dependent upon the position of the heating unit and hence upon the temperature condition of the stack.

A further object of the invention is the provision of compensated thermal elements controlling the main switch, both to eliminate deleterious effects of ambient temperatures and to enable a heat-producing unit to be employed to influence the thermal elements for operation of the main switch, which heat-producing unit need not be deenergized during cycling of the mechanism.

In the drawings:

Fig. 1 is a plan view of the mechanism with the thermal unit broken away;

Fig. 2 is a front; elevation;

Fig. 3 is a side elevation taken from the right of Figs. 1 and 2;

Fig. 4 is a horizontal section taken on the line 4-4 of Fig. 2;

Fig. 5 is a horizontal section taken on the line 5-4 of Fig. 2;

Fig. 6 is a vertical section taken on the line 8-8 of Fig. 2;

Fig. 7 is a vertical section taken on the line l-| of Fig. 2 and is similar to the top part of Fig. 6 but looking in the other direction;

Fig. 8 is a horizontal section taken on the line 8-8 of Fig. 2;

Fig. 9 is a vertical section taken on the line 9-4 of Figs-l and 2;

Fig. 10 is a vertical section taken on the line |lii0 of Fig. 1;

Fig. 11 is a horizontal section taken on the line l|li of Fig. 10; and,

Fig. 12 is a wiring diagram of the mechanism.

The mechanism includes a box portion II from the back of which there extends a supporting tube It rigidly attached to the box. At the outer end of the tube It is attached one end of a helical bimetal I1, the outer end of which is fixed to a driving shaft I3 that passes axially through the helix, the tube, and the box, and having a reduced portion l9, projecting from the front wall 28 of the box.

Through the wall 20 and about the rod I8 is a sleeve 2|. the flange of which extends flush with the shoulder marking the beginning of the reduced portion IQ of the rod l8.

Against this shoulder and over the reduced portion l8, there is disposed a friction disc 22 having integrally formed therewith a sleeve portion 23 that extends toward the end of the portion l9. Over the sleeve 23 and against the disc 22 is the upper end 24 of a heater-carrying arm, outside of which is a second friction disc 25 also disposed over the sleeve 23. An S-shaped leaf spring 26 fits over the sleeve 23, bears against the disc 25 and is held in place by a collar 21. A pin 28 passes through the collar 21, the sleeve 23 and the portion' [8 of the shaft II. It thus may be seen that a friction clutch is provided causing the member 24 normally to rotate with the shaft l8 but movable relative thereto against the friction of the two discs 22 and 25 produced by the spring 26.

The member 24 has a depending arm 30 thereon that projects downwardly therefrom. It has a slot 3| over a pin 32, the pin being secured to the front plate 20, and thereby limiting movement of the arm 30.

A heater-carrying plate is attached to one edge of the arm 38, there being feet 36 and 31 turned at 90 from the blade 35 and secured by screws 38 and 39 to the arm- 30. A low resistance heater coil 48 is wrapped around the blade 35 and the terminals of this heater coil are secured respectively to the screws 38. and 38. Flexible leads 42 and 43 extend from the screws 38 and 39 through slots 44 and 45 in the plate 28. The arcuate shape of the slots accommodates movement of the leads with the arm 30.

An additional arm 48 extends outwardly from the upper part of the member 24 in position to actuate a switch 49 by forcing a spring blade 50 into contact with the spring blade 5|. The normal springing of these blades causes the switch to open.

The depending arm 30 with its heater 4!! is oscillated by the helical bimetal il between two oppositely acting and mutually compensating bimetal strips 55 and 55 secured to a pivot block 56. The block is attached to a pivot 51, that in turn is secured to the front plate 20. A spacing collar 58 is provided about the pivot 51.

One end of the bimetal 54 is slotted at 59 to receive a point 60 projecting from the shoulder on an adjustable screw 6i threaded through an angle bracket 62 attached to the front plate 20. A look nut 63 holds the screw Si in adjusted position. The slot 59 permits displacement of the bimetal as it pivots about the pivot 51, as is shown in Fig. E.

The bimetal 55 controls a switch generally indicated at 65. This switch has two blades 66 and 6? that may be brought into contact with each other. The blade 6? is secured to a block 68 on the front plate 25 and has a terminal member 65 extending through the plate 25, to which is attached a lead An insulating block Ii passes over the blade 6i. The blade 66 is located on the opposite side of the insulating block Ii and it has a terminal member 12 extending through the front plate 20. The other end of lead 43 is attached thereto. An additional insulating block I4 passes outside the blade 66. Screwsl5 and I6 extend through the several blocks and blades as well as the front plate 20 to hold this switch thereto.

The two spring switch blades 56 and 61 are normally inherently urged apart to separate their contact elements. The top blade 66 has a projection 80 extending laterally from the outer end thereof to engage beneath a notch 8| in the bimetal 55. When normally engaged beneath the notch, the blade 66 is held down in contact with the blade 65, as in Fig. t When the bimetal pivots away from the projection 80, the inherent resiliency of the blade 66 moves it away from the blade 1, thereby opening the switch.

A reclosing button 83 has a reduced portion 84 passing through an opening 85 in the blade 66 and the slot 86 in the blade 6?. This arrangement provides a shoulder on one side of the blade 66 and a shoulder on the other side of the blade 6?, the first of these shoulders providing means for reengaging the blade 68 beneath the notch 8i on the bimetal 55 and the other shoulder preventing withdrawal of the button.

An angular cover plate 89 projects over the switch 65 to protect the same and has an opening 90 through which the button 83 projects.

As shown in Fig. 11, the switch blades 50 and 55 of the smaller switch 49 project through the front plate 20 and have leads 92 and 93 extending therefrom.

There are six terminals on the plate 20. The terminals 95 and 5B are connected across the power lines 97 and 98. The terminals 99 and I are connected externally with the leads IN and I02 to the burner ignition means BI, or the valve or other proper mechanism controlling the furnace. The terminals I03 and I04 are connected by the leads I and I06 to the room thermostat T.

Referring to Fig. 12, the internal connections may be seen. A primary I08 of a transformer (located within the box I5) is connected directly across the terminals 95 and 96 by leads I09 and H0. The terminals 96 and 99 are connected in series by a lead III. The terminal 95 is con-- nected in series with the terminal I00 by a lead H2 that passes through one side I I3 of a relay H4 and thence by a lead I I5 to the terminal I00.

The secondary H6 of the transformer has a lead I I1 passing through the coil I I8 of the relay I I4 and thence by a lead I iii to the terminal I04, whence the coil is put in series with the room thermostat T. From the terminal I03 there extends a lead I to a junction I2I. One lead I22 from this junction leads through the other side I23 of the relay and thence by line I24 to a Junetion I25. From this junction I extends the flexible lead 42 attached to one end of the heater 40. The other end of the heater by lead extends to switch blade 66 connected with the switch blade 61, which, by lead I0, is connected to the return end of the primary I I6.

From the junction I25, the lead 02 leads to the blade of the switch 49 and through the other blade 5i and the lead 93 to the junction I2I.

Operation will also be assumed that the room thermostat is open. The stack temperature will be low, hence the coil I'i' cold so that the rod I8 and with it the arm 30 are rotated through a maximum distance in a counterclockwise direction, viewed in Figs. 2 and 12. In this position, the heater 40 is disposed adjacent the bimetal 55. Likewise the switch 48 is closed through the action of the arm 40 in its most counterclockwise position. The switch 65 is closed by engagement with the bimetal 55.

The first change will occur in the event the room thermostat closes. demanding heat. In this case, current will flow from the secondary H6 through the line N1, the coil II8, the line H9, the terminal I04, the line I05, the thermostat T, the line I05, the terminal I 03, the line I20, the junction I2I, the line 93, the switch 40, the line 92, the junction I25, the line 42, the heater 40, the line 43, the switch 65 and the line I0 to the opposite end of the secondary. This causes the heater to be energized and also closes the relays H3 and I23. When the relay III is closed, the igniter BI is put across the line as follows: line 91, terminal 95, line I09, line II2, relay II3, line II5, terminal I00, line I02, the igniter, line IOI, terminal 99, line III, terminal 06, and line 88. The furnace will then start supplying heat both to the stack, almost instantly, and more slowly to the room wherein the thermostat Tis located.

As the stack heats, the helical bimetal II turns the shaft I8 in a clockwise direction, withdrawing the heater from its position in proximity to the bimetal to a middle position between the two bimetals 55 and 54, in which position the bimetals act oppositely and preserve the status of the switch 65. If the helix II deflects more than the degree of rotation permitted by the slot ll, the slip clutch admits of relative movement between the shaft I8 and the arm 30.

In normal cycling, the furance will ultimately warm the thermostat T, which then will open. This deenergizes the heater and the relay 4, and by the latter, the igniter BI. The stack will cool in due course, bringing the arm 30 and heater 40 to starting position near the bimetal 55. Since the movement of the helix I1 between the maximum and minimum of normal operation ismuch greater than the permitted movement of the arm 30, that arm is in starting position very early in the cooling stage of the stack, and in its operating position between the bimctals very early in the heating stage of the stack. Thus proper cycling may be initiated in both directions from practically any stack temperature.

It is evident that the switch 49 is opened when the stack has heated causing displacement of the arms 30 and 48. If the stack is hot, such as caused by periodic operation of the furnace, but the effect of the operation has not yet reached the room thermostat, closing of the thermostat will produce no effect until the stack cools, because the circuit is open at both the switch 49 and the relay H3. The furnace cannot be overloaded.

11', when the room thermostat first closes, the stack does not heat, owing to a failure of ignition or the like, the arm 30 and the heater 40 will not be displaced. The time required for the heater to heat and act upon the bimetals is no less than the time normally required for the helix IT to be heated to remove the heater from the bimetal 55. But where the arm 30 remains near the bimetal 55 for an undue interval produced by failure of the stack to heat, the bimetal will move away from the blade 66 and permit the two blades 56 and 61 to springapart. Since the switch 65 controls the entire secondary circuit, that circuit will be deenergized. and relay H4 will open at both H3 and I23. The furnace will thereby be completely out off if the stack fails initially to heat.

I! the stack does heat, and having attained a certain temperature, improperly cools for any reason, the helix I! will deflect the heater toward the bimetal 55, and in due time cause this bimetal to release the switch t5- opening the circuits. ture is from which the drop begins, since the slip clutch action causes displacement of the heater upon any reduction in temperature of an amount sufflcient to displace the arm 30 toward the bimetal 55. The device thus operates upon change of temperature.

Whenever the switch 65 is opened, it may be closed again only by depressing the button 83. It will remain closed only if the bimetal 55 is at a normal temperature relative to that of the bimetal H.

It is immaterial what the stack tempera- What is claimed is:

1. In a mechanism of the kind described, a pair of spaced and oppositely acting bimetals joined for'pivotal movement together about a given point, said bimetals extending from such pivot point, an adjustable abutment for the free end of one bimetal, an actuated mechanism controlled by the iree end of the other bimetal, a heater, and means supporting the heater between the bimetals and movable toward one or the other thereof.

2. In a mechanism of the kind described, a base, a shaft thereon, means to displace the same about its axis, an arm on the shaft, a heater on the arm and pivotable therewith, a pair of oppositely acting thermal devices, means securing them together at one end and mounting them for pivotal movement on the base, means holding the free end of one means actuated by the free end of the other, the thermal devices being disposed one on each side of the heater, and the heater being movable toward one or the other thermal device.

3. In a mechanism of the kind described, a base, a shaft thereon, means to displace the same about its axis, an arm on the shaft, a heater on the arm and pivotable therewith, a pair of oppositely acting thermal devices, means securing them together at one end and mounting them for pivotal movement on the base, means holding the free end of one means actuated by the free end of the other, the thermal devices being disposed one on each side of the heater, and the heater being movable toward one or the other thermal device, a switch, and means on the arm to actuate the switch upon displacement of the arm.

4. In a mechanism of the kind described, a base, a shaft thereon, means to displace the shaft about its axis, an arm on the shaft, a heater on the arm and pivotable therewith, a pair of oppositely operating bimetallic strips, means connecting the strips together at one end and securing them pivotally to the base, means adiustably holding the free end 01 one strip against displacement, and means actuated by the free end of the other strip.

LAWRENCE M. PERSONS. 

